Traffic for mobile terminals (such as smartphones, feature phones, etc.) occupies most resources of recent networks. The amount of traffic used by mobile terminals tends to increase in the future as well.
Meanwhile, there is an increasing demand for a capability to respond to services with various requirement conditions, accompanying the development of IoT (Internet of things) services (such as transportation systems, smart meters, monitoring systems for devices, etc.). This leads to a demand for a technique that achieves a higher data rate, a greater capacity, and a smaller delay in a next-generation communication standard (for example 5G (Fifth Generation Mobile Communications)) in addition to the 4G (Fourth Generation Mobile Communications) standard techniques (for example Non-Patent Documents 1 through 11). Note that working groups of the 3GPP are discussing next-generation communication standards (such as for example TSG-RAN WG1, TSG-RAN WG2, etc.) (Non-Patent Documents 12 through 18).
Further, in order to provide a variety kinds of services, many use cases that are classified into Enhanced Mobile Broadband (eMBB), massive Machine Type Communications (mMTC), Ultra-Reliable and Low Latency Communication (URLLC), and others are proposed to be supported in the 5G.
LTE (Fourth Generation Communications scheme) etc. employ a technique of hybrid automatic repeat request (HARQ) to implement highly efficient data transport. According to HARQ, for example, a receiver requests a source device to perform a retransmission when received data was not successfully decoded in a process based on a layer-1 protocol such as LTE etc. In response to the request for the data retransmission, the source device transmits retransmission data corresponding to the data that was not successfully decoded in the receiver. The receiver combines the data that was not successfully decoded and the retransmission data so as to decode the data. This enables highly efficient and highly accurate retransmission control. Note that when the receiver decodes data successfully, the receiver transmits ACK information to the source device, and when the receiver fails to decode data successfully, the receiver transmits NACK information to the source device.
Incidentally, 1-bit feedback information that represents ACK/NACK is reported for, for example, a 14-symbol Transmission Time Interval (TTI) in recent LTE-based wireless communication systems. Also, a group of the 3GPP agreed to a scheme in which feedback information that represents ACK/NACK is reported for each code block group (Code Block Group or CBG) (Non-Patent Document 13). In that case, feedback information for each code block group uses one bit. Also, the number of symbols that forms a code block group is for example smaller than or equal to 14.